Custom fields instructions

I am trying to find a way to put instructions under a text field in Custom Registration/Profile Fields

Like under a email field put in “A valid e-mail address. All e-mails from the system will be sent to this address. The e-mail address is not made public and will only be used if you wish to receive a new password or wish to receive certain news or notifications by e-mail.”

And under an Address Field put “Please enter your full mailing address including your unit number (if applicable), street address, street name, city, province, postal code (or ZIP), and country.”